Full lightfield with monocular and stereoscopic depth control via monocular-to-binocular hybridization

ABSTRACT

An optical subsystem for use in a display system or an imaging system comprises a plurality of reflective surfaces collectively arranged to provide variable control of device-internal path lengths of light coming to an imaging sensor or traveling a path to an eye of a viewer. The optical subsystem can be used to provide multiple images concurrently at different apparent depths as perceived by the user.

This is a continuation-in-part of U.S. patent application Ser. No.17/810,567, filed on Jul. 1, 2022, and titled, “Display Systems andImaging Systems with Dynamically Controllable Optical Path Lengths,”which is incorporated by reference herein.

TECHNICAL FIELD

This application generally relates generally to lightfield displays andimaging apparatuses, and more specifically, to dynamically controllingthe optical path of light emitted within a lightfield display or imagingapparatuses to affect the image produced or captured thereby.

BACKGROUND

In today's society, there has been increasing movement towards moreimmersive light-field and/or autostereoscopic three-dimensional (3D)displays, due to advancement in electronics and microfabrications. Mostcurrent and common autostereoscopic 3D displays can require virtualreality (VR) headgear or similar devices. However, VR headgear can causeeye strain and other similarly-related fatigue issues. These issuesoccur due to two primary issues with current and common VR headgear.Firstly, most common and current VR headgear divide the image into twoviewing zones in which parallax is extracted from those viewing zonesand overlapped to procure a seemingly single, whole image. Secondly,most current and common VR headgear have the viewing zones too near tothe user's eyes. Another issue with most current and common VR headgearis the binocular gaps in the image projected due to the images being fedinto two separate viewing zones, one for each eye of the user withseparate optics.

Recent advances in display technology include the use of concentriclightfield technology to create large field-of-view (FOV) immersive 3Ddisplays. However, even the most recent display technologies facevarious design challenges, such as reducing the form factor of thedisplay without sacrificing (or while increasing) the size of theheadbox, reducing distortion, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 illustrates a set of elements that can compose variousembodiments of field evolving cavities (FECs) described in thisdisclosure.

FIGS. 2A through 2C illustrate various arrangements of the elements fromFIG. 1 to produce different architectures of the FEC embodimentsdescribed herein.

FIG. 3A illustrates a perspective view of an example embodimentincluding multiple switchable stacks for depth modulation.

FIG. 3B illustrates a perspective view of an example embodimentincluding a compressed cavity.

FIG. 3C illustrates a perspective view of an example embodimentincluding multiple seed display panels.

FIG. 3D illustrates a perspective view of an example embodimentincluding a 1D-1D geometry.

FIG. 3E is another view of the embodiment of FIG. 3A in which themulti-layered components are shown in “exploded” form.

FIG. 3F is another view of the embodiment of FIG. 3B in which themulti-layered components are shown in “exploded” form.

FIG. 3G is another view of the embodiment of FIG. 3C in which themulti-layered components are shown in “exploded” form.

FIG. 3H is another view of the embodiment of FIG. 3D in which themulti-layered components are shown in “exploded” form.

FIG. 4A illustrates block-diagram representations of a process thattakes 2D or 3D content and produces a three-dimensional display.

FIG. 4B illustrates block-diagram representations of a process thatcaptures and records 3D images of scenes into a computer.

FIGS. 5A through 5K illustrate a set of side views of exampleembodiments the using the switchable stacks of FIG. 3A in multipleconfigurations and with various switchable elements.

FIGS. 6A through 6K illustrate a set of side views of exampleembodiments to produce the compressed displays from FIG. 3B or thefractional lightfield displays for increased headbox space andtessellated virtual images.

FIGS. 7A through 7F illustrate a set of side views of exampleembodiments using multiple seed panels from FIG. 3C with single- andhigher-order FECs.

FIGS. 8A through 8P illustrate a set of side views of exampleembodiments using various 1D-1D architectures, generalized from FIG. 3D,and include both static and mechanically modulated layers.

FIGS. 9A and 9B illustrate two simulated ray diagrams that demonstratean increased headbox space and longer eye distance for a display systemwith multiple light reflections within a cavity compared to those for adisplay with a single reflection.

FIGS. 10A and 10B illustrate simulated ray diagrams for 1D-1D cavities.

FIGS. 11A through 11C illustrate schematically the manufacturing of somesubsampled diffractive elements.

FIGS. 12A through 12D illustrate varieties of headset displays thatserve as examples of additional embodiments of the display system andits integration with stereoscopic display methods.

FIGS. 13A through 13C illustrate portable additional embodiments thatcan be implemented in automobiles or in smart devices for a variety ofapplications in different configurations.

FIG. 14 is a flowchart illustrating a process associated with thetechniques introduced here.

FIGS. 15A and 15B illustrate two different perspective views of anexample headset incorporating display technology such as introducedherein.

FIG. 15C illustrates a headset displaying multiple virtual objects atdifferent virtual depths.

DETAILED DESCRIPTION

In this description, references to an “embodiment,” “one embodiment” orsimilar words or phrases mean that the feature, function, structure, orcharacteristic being described is an example. Occurrences of suchphrases in this specification do not necessarily all refer to the sameembodiment. On the other hand, the embodiments referred herein also arenot necessarily mutually exclusive.

All illustrations and drawings describe selected versions of thetechniques introduced here and are not intended to limit the scope ofthe techniques introduced here. All references to “user” or “users”pertain to either individual or individuals who would utilize thetechniques introduced here.

Concentric lightfield displays provide depth perception to the users atthe monocular level by manipulating optical wavefronts by using fieldevolving cavities (FECs). FECs are described in detail in U.S. PatentApplication Publication Nos. 2020/0150453, 2021/0103160, 2021/0356760,and in U.S. Pat. No. 10,768,442, all of which are incorporated byreference herein in their entireties, and henceforth referred to hereinas references [1], [2], [3] and [4], respectively. Concentric lightfielddisplays are also described in detail in at least reference [4]. Thismechanism enables optical depth modulation, effectively eliminates theaccommodation-vergence mismatch for comfortable viewing, andsignificantly reduces user eye stress and fatigue. The techniquesintroduced herein FECs with active-material layers, a shield layer,multiple seed display panels, and multiple one-dimensional (1D-1D)curved optical structures. These types of displays can provide tunableoptical depth modulation and full or partial (fractional) lightfieldsignaling functionality, which reduce the overall system footprint andprovide the ability to multiplex information in depth across the fieldof view with increased signal-to-noise performance. The term“one-dimensional” (1D) in this context refers to that characteristic bywhich an optic has optical focusing power in one dimension. The term“1D-1D curved” as used herein means an optical characteristic by whichan optic has multiple separate layers of curvature that are orthogonalto each other. For example, a reflector can have Fresnel lensing thatprovides an effective curvature about a first axis, on top of areflective structure that is physically curved along a second axis thatis orthogonal to the first axis.

This approach can be contrasted with the four main existing lightfielddisplay methods—super multi-view, computational, holographic, andmulti-focal—each with its own associated strengths and weaknesses (seereferences [1], [2], [3] and [4]). Super multi-view lightfield displayscan be realized in a compact form factor but are limited in resolutionwith a reduced and restricted viewable zone. Computational approachesprovide a mechanism to increase the resolution but produce haze andsuffer from temporal flickering artifacts. Typical issues using theholographic method involve significant color nonuniformity and fringingor specular artifacts. In contrast, multi-focal lightfield displaymethods can provide clean images but are typically bulky with a largeform factor. Aside from these issues, all current lightfield displaymethods typically suffer from large bandwidth requirements, a relianceon expensive and/or advanced components—such as tunable lenses—that arenot easily produced at scale, poor color uniformity, small field of viewor viewable zone, small aperture, low brightness, haze and diffractionartifacts, limited depth range, lack of compatibility with existingdisplay drivers, bulkiness, and the occasional necessity to wearspecialized glasses. Correspondingly, these limitations and challengeshave limited the adoption and production of lightfield displays incommercial and/or enterprise settings and applications. Based on theselimitations, new techniques are desired that are more compact,manufacturable at lower cost, and able provide larger viewable zonesmore comfortably.

This disclosure introduces different lightfield display embodiments andsystems using tunable, compressed FECs and fractional lightfieldsignaling. Introduced herein are four main architectures:

-   -   1) FEC cavity design for tuning optical depth in a fractional        lightfield display, in which the depth is controlled in small        increments by using a stack of switchable reflectors;    -   2) compressed design in which the optical path of the object to        the curved reflector is increased while keeping the thickness of        the apparatus thin;    -   3) multiple-display design to support multiple depth layers by        using multiple individual displays on different sides of the        optical cavity; and    -   4) alternate FEC embodiments using 1D-1D bent optical surfaces        and diffractive optical elements (DOEs) to mimic 2D imaging        effects for optical wavefront control by using components with        relaxed manufacturing tolerances and complexity.

This disclosure then describes the content depth-layer mapping approachfor both imaging and display applications of such cavities. It thendiscloses embodiments for each of the four above-mentionedarchitectures. This disclosure also describes the modulation of acousticor mechanical waves onto 1D-1D architectures such that the compositionof these mechanical waves, or macroformings, on the reflective surfacescreate compound lensing effects to control the optical wavefront indifferent architectures of FECs. This disclosure also describes hybrid1D-1D approaches such that the lensing effects or wavefront effects arecreated by geometrical forming on one dimension and is done bydiffractive or refractive approaches in the other, perpendicular,dimension to provide an equivalent of two-dimensionally curved(“2D-curved”) reflectors or surfaces (a “2D-curved” reflector is areflector that has curvature about two orthogonal axes). It furtherdiscloses some applications of these embodiments for in-vehiclevisualization apparatuses, hand watches and various other scenarios.

Nomenclature

In this disclosure, the term “arbitrarily engineered” means being of anyshape, size, material, feature, type, kind, orientation, location,quantity, construction, composition, components, and arrangements ofcomponents with a single or array of components, that would allow thedescribed technique or that specific component to fulfill theobjective(s) and purpose(s) of the technique or that specific component.

In this disclosure, “lightfield” at a plane means a vector field thatdescribes the amount of light flowing in every or several selecteddirections through every point in that plane. “Lightfield” is thedescription of angle and intensity of light rays traveling through oremitted from that plane. In this disclosure a fractional lightfieldmeans a subsampled version of the full lightfield such that the fulllightfield vector field is represented by a limited number of samples indifferent focal planes and/or angles.

In this disclosure, “depth modulation” means the change, programming, orvariation of monocular optical depth of the display or image. “Monocularoptical depth” is the optical depth that directly relates to theperceived distance between the user and the source of light. An idealsource of light emits light rays equally in all directions, and thecollection of light rays can be understood to lie on sphere, called awavefront, of expanding radius. When an emissive image (e.g., anilluminated object or a display) is moved farther away from an observer,the emitted light travels a longer distance, and the user observes aspherical wavefront of larger radius and correspondingly smallercurvature, i.e., the wavefront is viewed as flatter. This reduction inthe curvature is perceived by the eye or camera as a deeper depth.Monocular optical depth does not require both eyes or stereopsis to beperceived. Evolution of a wavefront means changes in wavefront curvaturebecause of optical propagation.

In this disclosure, the term “optically coupled” means one element beingadapted to impart, transfer, feed, or direct light to another elementdirectly or indirectly.

In this disclosure, the term “chief rays” means the center axis of thelight cone that comes from a particular pixel or point in space.

In this disclosure, the terms “Field evolving cavity” and “FEC” mean anon-resonant (e.g., unstable) cavity that allows light to reflect backand forth within its reflectors to evolve the shape of the wavefrontassociated with the light in a physical space. One example of an FEC maycomprise two or more half-mirrors or semi-transparent mirrors facingeach other. As described herein, an FEC may be parallel to a displayplane (in the case of display systems) or an entrance pupil plane (inthe case of imaging systems). An FEC may be used for changing theapparent depth of a display or of a section of the display. In an FEC,the light bounces back and forth, or circulates, between the facets ofthe cavity. Each of these propagations is referred to as a “pass.” Forexample, suppose there are two reflectors for the FEC, one at the lightsource side and one at the exit side. The first instance of lightpropagating from the entrance reflector to the exit reflector is calleda forward pass. When the light or part of light is reflected back fromthe exit facet to the entrance facet, that propagation is called abackward pass, as the light is propagating backward toward the lightsource. In a cavity, a round trip occurs once the light completes onecycle and comes back to the entrance facet. FECs can have many differentarchitectures, but the principle remains the same. An FEC is an opticalarchitecture that creates multiple paths for light to travel, either byforcing light to go through a higher number of round trips or by forcinglight from different sections of the same display to travel differentdistances before they exit the cavity. If the light exits the cavityperpendicular to the angle it entered the cavity, the FEC is referred toas an off-axis FEC or an “FEC with perpendicular emission.”

In this disclosure, the term “round trips” denotes the number of timesthat light circulates or bounces back and forth between the entrance andexit facets or layers of a cavity.

In this disclosure, the “aperture of a display system” is the surfacewhere the light exits the display system toward the exit pupil of thedisplay system. The aperture is a physical surface, whereas the exitpupil is an imaginary surface that may or may not be superimposed on theaperture. After the exit pupil, the light enters the outside world.

In this disclosure, the “aperture for imaging systems” is the area orsurface where the light enters the imaging system after the entrancepupil of the imaging system and propagates toward the sensor. Theentrance pupil is an imaginary surface or plane where the light firstenters the imaging system.

In this disclosure, the term “display” means any element that emitslight that forms (at least in part) an image to be displayed to a user.Hence, the term “display” means an “emissive display,” which can bebased on any technology, including, but not limited to, liquid crystaldisplays (LCD), thin-film transistor (TFT), light emitting diode (LED),organic light emitting diode arrays (OLED), active matrix organic lightemitting diode (AMOLED), plastic organic light emitting diode (POLED),micro organic light emitting diode (MOLED), or projection orangular-projection arrays on flat screens or angle-dependent diffusivescreens or any other display technology and/or mirrors and/or halfmirrors and/or switchable mirrors or liquid crystal sheets arranged andassembled in such a way as to exit bundles of light with a divergenceapex at different depths or one depth from the core plane orwaveguide-based displays. Unless stated otherwise, the display may be anautostereoscopic display that provides stereoscopic depth with orwithout glasses. It might be curved or flat or bent or an array ofsmaller displays tiled together in an arbitrary configuration. Thedisplay may be a near-eye display for a headset, a near-head display orfar-standing display. The application of the display does not impact theprinciple of the techniques introduced here.

In this disclosure, the “angular profiling” means the engineering oflight rays to travel in specified directions. It may be achieved byholographic optical elements (HOEs), diffractive optical elements(DOEs), lenses, concave or convex mirrors, lens arrays, microlensarrays, aperture arrays, optical phase masks or amplitude masks, digitalmirror devices (DMDs), spatial light modulators (SLMs), metasurfaces,diffraction gratings, interferometric films, privacy films, or othermethods. The intensity profiling may be achieved by absorptive orreflective polarizers, absorptive coatings, gradient coatings, or othermethods. The color or wavelength profiling may be achieved by colorfilters, absorptive notch filters, interference thin films, or othermethods. The polarization profiling might be done by metasurfaces withmetallic or dielectric materials, micro- or nano-structures, wire grids,absorptive polarizers, quarter-wave plates, half-wave plates, 1/x-waveplates, or other nonlinear crystals with an isotropy, orspatially-profiled waveplates.

In this disclosure, the terms “active design,” “active components,” or,generally, “active” mean a design or component that has variable opticalproperties that can be changed with an optical or electrical signal.Electro-optical (EO) materials include liquid crystals (LC); liquidcrystal as variable retarder (LCVR); or piezoelectric materials/layersexhibiting Pockel's effects (also known as electro-optical refractiveindex variation)—such as lithium niobate (LiNbO3), lithium tantalate(LiTaO3), potassium titanyl phosphate (KTP), strontium barium niobate(SBN), and β-barium borate (BBO)—with transparent electrodes on bothsides to introduce electric fields to change the refractive index. TheEO material can be arbitrarily engineered. Passive designs or componentsare referred to as designs that do not have any active component otherthan the display.

In this disclosure the “pass angle” of a polarizer means the angle atwhich the incident light normally incident to the surface of thepolarizer can pass through the polarizer with maximum intensity. Twoitems that are “cross polarized” are such that their polarizationstatuses or orientations are orthogonal to each other. For example, whentwo linear polarizers are cross polarized, their pass angles differ by90 degrees.

In this disclosure, “reflective polarizer” means a polarizer that allowsthe light that has its polarization aligned with the pass angle of thepolarizer to transmit through the polarizer and that reflects the lightthat is cross polarized with its pass axis. A “wire grid polarizer” (areflective polarizer made with nano wires aligned in parallel) is anexample of such polarizer. An “absorptive polarizer” is a polarizer thatallows the light with polarization aligned with the pass angle of thepolarizer to pass through and that absorbs the cross polarized light. A“beam splitter” is a semi-reflective layer that reflects a certaindesired percentage of the intensity of the light, which can be dependenton its polarization, and passes the rest of the light. A simple exampleof a beam splitter is a glass slab with a semi-transparent silvercoating or dielectric coating on it and that allows 50% of the light topass through it, and reflects the other 50%.

In this disclosure, an “imaging sensor” may use arbitrary image sensingtechnologies to capture light or a certain parameter of light that isexposed onto it. Examples of such arbitrary image sensing technologiesinclude complementary-symmetry metal-oxide-semiconductor (CMOS), singlephoton avalanche diode (SPAD) array, charge-coupled Device (CCD),intensified charge-coupled device (ICCD), ultrafast streak sensor,time-of-flight sensor (ToF), Schottky diodes, or any other light orelectromagnetic sensing mechanism for shorter or longer wavelengths.

As used herein, “imaging system” means any apparatus that acquires animage that is a matrix of information about light intensity and/or itsphase, temporal, spectral, polarization, entanglement, or otherproperties used in any application or framework. Imagining systemsinclude cellphone cameras, industrial cameras, photography orvideography cameras, microscopes, telescopes, spectrometers,time-of-flight cameras, ultrafast cameras, thermal cameras, or any othertype of imaging system.

In this disclosure, the term “macroforming” means shaping thegeometry/curvature of an optical element's surface or surfaces where theoptical features have a periodicity of at least one millimeter (incontrast with “microforming,” in which the optical features have aperiodicity of less than one millimeter and which creates subwavelengthstructure).

The techniques introduced here build upon certain aspects of thepreviously described display systems (see references [1], [2], [3] and[4]), which generate a high-quality virtual image, which may be a 2D,stereoscopic 3D, and/or multifocal image, where the display system hasan intended (designed) viewing point for the human viewer that is atleast 10 cm from the display (in contrast with conventionalhead-mountable displays (HMDs)). The techniques introduced here extendearlier techniques that produce a single, contiguous lightfield thatenables simultaneous detection of monocular depth by each eye of thehuman viewer, where the monocular depth can be greater than the actualdistance of the display from the human viewer and provides an apparentsize of the display (as perceived by the human viewer) that is largerthan the actual size of the display when the human viewer is located atthe intended viewing point. With the techniques introduced here, theaccessible monocular depth is also dynamically tunable in terms of depthlocation and profile, and the number of depth layers created across theuser field of view, in contrast with current autostereoscopic displays,is not fixed at the physical location of the surface of the displaypanel. Note that any of the techniques introduced below can be adaptedor modified to create an imaging system (e.g., a camera system) capableof creating multi-layer, multi-zoomable images; this can be accomplishedby replacing the active display element(s) (e.g., LEDs orsimilarly-purposed elements) with one or more optical sensors (e.g.,CCDs or similarly-purposed elements), while otherwise retaining the samephysical/optical configurations described below.

In some embodiments, a display system in accordance with the techniquesintroduced here is designed to be positioned about 20 cm from theviewer's eyes and to provide an apparent display size (i.e., asperceived by the human viewer) of approximately 100 inches diagonally,where 10% of the peripheral virtual screen at the edges of the field ofview has different modulated image depths than the central region, orwhere multiple depth levels are present at different parts of the fieldof view. In this context, “horizontally” means parallel to an imaginaryline that passes through the geometric centers of the human viewer's twoeyes when the human viewer is viewing the display in the normal(intended) manner.

The techniques introduced here allow production of a concentric lightfield with monocular-to-binocular hybridization, adding depth modulationtunability and fractional lightfield signaling capabilities and usingcompressed FEC embodiments with 1D-1D and DOE components to reducemanufacturing complexity and to decrease system size. The term“concentric light field” (also called “curving light field”) as usedherein means a light field in which, for any two pixels of the displayat a fixed radius from the viewer (called “first pixel” and “secondpixel”), the chief ray of the light cone emitted from the first pixel ina direction perpendicular to the surface of the display at the firstpixel intersects with the chief ray of the light cone emitted from thesecond pixel in a direction perpendicular to the surface of the displayat the second pixel. A concentric light field produces an image that isfocusable to the eye at all points, including pixels that are far fromthe optical axis of the system (the center of curvature), where theimage is curved rather than flat, and the image is viewable within aspecific viewing space (headbox) in front of the lightfield.

FIG. 1 shows a number of basic “building block” components of theembodiments discussed herein. These components can be arbitrarilyengineered. Element 1 is the schematic representation of an emissivedisplay. Element 2 is the representation of a sensor, which can be anoptical sensor, a camera sensor, a motion sensor or generally an imagingsensor. Element 3 is the schematic representation of a mirror, which canbe a first-surface mirror, or second-surface mirror, or generally anyreflective surface, Element 4 is a freeform optic; this elementrepresents any freeform optic, convex or concave or neither, expressedwith spherical, elliptical, conjugate, polynomial, hyperbolic or anyother convex or concave or arbitrary function. Element 5 is therepresentation of curved display. Element 6 is the representation of anelectro-optic material such as liquid crystals (LC). Element 7represents an electro-optical (EO) polarization rotator such that byvariation of signal voltage, a linear polarization can be rotated todesired angle. Element 8 is an absorptive polarizer such that onepolarization of the light passes through, and the perpendicularpolarization of light is absorbed.

Element 9 is a half-wave plate (HWP), which produces a relative phaseshift of 180 degrees between perpendicular polarization components thatpropagate through it. For linearly polarized light, the effect is torotate the polarization direction by an amount equal to twice the anglebetween the initial polarization direction and the axis of thewaveplate. Element 10 is quarter-wave plate (QWP), which produces arelative phase shift of 90 degrees. It transforms linearly polarizedlight into circularly polarized light, and it transforms circularlypolarized light into linearly polarized light.

Element 11 is an angular profiling layer, which is an arbitrarilyengineered layer to produce a specified angular distribution of lightrays.

Element 12 is a liquid crystal (LC) plate that is switched “ON.” In thisstate, the LC plate rotates the polarization of the light that passesthrough it. Element 13 is an LC plate that is switched “OFF,” such thatin this OFF state the state of the light polarization is unchanged upontransmission through the LC plate.

Element 14 is a diffractive optical element (DOE), which hasmicrostructure to produce diffractive effects. The DOE can be of anymaterial.

Element 15 is a mechanical actuator that can physically move theelements to which is connected via an electrical or other types ofsignals.

Element 16 is a full switchable mirror in the “ON” configuration, andelement 17 is a full switchable mirror in the “OFF” configuration. Whenthe switchable mirror is ON, it is reflective. When it is OFF, it istransparent. The mirror can also be in a semitransparent state.

Element 18 is a retroreflector, which is a mirror that reflects lightrays in the exact same directions along which they are incident. Theretroreflector can be fabricated with microstructure such asmicrospheres or micro corner cubes or metasurface stacks, or it can be anonlinear element.

Element 19 is a beam splitter, which partially reflects and partiallytransmits light. The ratio of reflected light to transmitted light canbe arbitrarily engineered.

Element 20 is a polarization-dependent beam splitter (PBS). It reflectslight of one polarization and transmits light of the orthogonalpolarization. A PBS can be arbitrarily engineered and made usingreflective polymer stacks or nanowire grids or thin film technologies.

Element 21 is a lens group, which includes one or multiple lenses ofarbitrary focal length, concavity, and orientation.

Element 22 is a one-dimensional (1D) bent optic. It is a structure thatis curved or arbitrarily engineered in one direction but is uniform inthe perpendicular direction.

Element 23 represents a light ray that is x-polarized. Its polarizationdirection is in the plane of the page of side-view sketches. Element 24represents a light ray that is y-polarized, orthogonal to Element 23.Its polarization direction is perpendicular to plane of side-viewembodiment sketches. Element 25 represents a light ray that iscircularly polarized. Such light contains both x- and y-polarized lightsuch that the two components are out of phase by 90 degrees, and theresulting polarization direction traces out a circle as the lightpropagates. The circular polarization can be clockwise or right circularpolarization (RCP) or counter clockwise or left-handed circularpolarization (LCP).

Element 26 represents an electrical signal that is used in theelectrical system that accompanies the display system to modulate theoptical elements or provide feedback to the computer.

Element 27 is an antireflection (AR) layer that is designed to eliminatereflections of light incident on its surface. Element 28 is anabsorptive layer that absorbs all incident light. Element 29 is amicro-curtain layer that acts to redirect light into specifieddirections or to shield light from traveling in specified directions. Amicro curtain can be made by embedding thin periodic absorptive layersin a polymer or glass substrate, or it can be made by fusing thin blackcoated glass and cutting cross-sectional slabs.

The basic elements in FIG. 1 can be combined to produce the functionalelements or subassemblies or sub-systems shown in FIGS. 2A through 2C.In FIG. 2A, element 30 (QBQ) comprises a QWP, beam splitter, thenanother QWP. Element 31 (QM) comprises a QWP layered on top of a mirror.It reflects all light, and it converts x-polarized light intoy-polarized light and y-polarized light into x-polarized light. It doesnot change circularly polarized light.

Element 32 is an electro-optic shutter, which includes an LC layer andan absorptive polarizer. When the LC is ON, it rotates the polarizedincident light such that it is aligned perpendicular to the absorptivepolarizer and is absorbed by it. When the LC layer is OFF, it leaves thepolarization unchanged and parallel to the absorptive polarizer whichtransmits it. Element 33 is an electro-optic reflector, which includesan LC layer and a PBS. When the LC layer is ON, it rotates thepolarization such that it aligned along the transmit orientation of thePBS. When the LC layer is OFF, the light passing through it is alignedsuch that it is reflected by the PBS.

Element 34 is a full switchable black mirror (FSBM). In the ON state,the full switchable mirror is on and reflects light of allpolarizations. In the OFF state, the switchable layer and absorptivelayer together extinguish x-polarized light, transmits y-polarizedlight, and transmits only the y-component of circularly polarized light.Element 35 is a full switchable black mirror with quarter-wave plate(FSBMQ) and includes a FSBM with an added QWP layer. In the ON state, itreflects all light and interchanges x-polarized with y-polarized light.It reflects circularly polarized light unchanged. In the OFF state itextinguishes circularly-polarized light, transmits y-polarized light,and coverts x-polarized light into y-polarized light and transmits theresult.

Shown in FIG. 2B are two switchable reflective stacks. Element 36 is aswitchable black mirror with quarter-wave plate (SBMQ) including a QWP,followed by two alternating layers of LC and PBS, and one absorptivepolarizer. The difference between full switchable mirror (FSBMQ) andswitchable mirror (SBMQ) is the dependency of reflectivity topolarization. In the former, the full switchable mirror, the totalreflectivity of the material is changing, agnostic to the polarizationof the incident light, whereas the latter object allows for apolarization-dependent reflectivity.

For element 36, when both LC layers are OFF (transmit mode), allincident polarizations transmit an x-polarized component. When the firstLC layer is ON and the second OFF (reflect mode), circularly polarizedlight is reflected unchanged, y-polarized light is reflected asx-polarized light, and x-polarized light is reflected as y-polarizedlight. When the first LC layer is OFF and the second LC is ON (absorbmode), all the incident light strikes the absorptive layer and isextinguished, and no light is transmitted through the layers.

Element 37 is an electro-optical reflector stack (EORS), including astack of N alternating PBS and LC layers. All but one LC layer are inthe OFF state, and the LC layer that is in the ON state reflects theincident x-polarized light. All other layers transmit the light. Byvarying which LC layer is in the ON state, the EORS modulates theoptical depth or optical path or the length that the light has to travelthrough the stack before it is reflected by a cross-polarized PBS layernext to the ON LC layer.

Shown in FIG. 2C are combinations of elements that form a variety offield evolving cavities (FEC) or layer stacks that can be used assubsystems for architectures explained throughout the disclosure.Elements 38 and 39 are OFF and ON states, respectively, of a display andQBQ followed by an electro-optic reflector. Here, in the OFF state, thelight directly exits the aperture. In the ON state, the light is forcedto travel one round trip in the cavity, and the displayed image appearsto be deeper compared to the actual location of the display. Element 40is a display followed by a QBQ and a PBS set on a mechanical actuator.The actuator shifts the set of layers to create longer or shorteroptical path lengths for the light. Element 41 is a mechanical actuatorfixed to a display. The actuator can shift or macroform the displayrelative to an angular profiling layer to force the light to changedirectionality or to become more or less collimated. In someembodiments, the angular profiling layer might be a lenslet array suchthat the mechanical movement of the display changes the object distanceand therefore impact the collimation. In some embodiments, the displaymight be macroformed, meaning it may have mechanical waves or bendsinduced onto it by the mechanical actuators so that the directionalityor collimation of the light that comes out of the angular lenslet arrayis impacted in a desired way.

In some embodiments, the display might be mechanically shifting, becauseof the actuator's motion along a translational axis, again to impact thedirectionality of the exit light from the apertures. The mechanicalactuation mechanism might be arbitrarily engineered. In someembodiments, the mechanical actuator might be an array of ultrasonictransducers; in some embodiments, the mechanical translation might bedone by a high rotation-per-minute brushless motor; in some embodiments,the mechanical movements might be delivered via a piezo- or steppermotor-based mechanism.

Element 42 is a cavity that includes a display that is partitioned intosegments. Light from the bottom segment is reflected by a mirror, andlight from the upper segments are reflected by subsequent beamsplitters. An absorptive layer absorbs unwanted stray light. This is anexample of an off-axis FEC. The FEC can be arbitrarily engineered torepresent desired number of layers (see references [1], [2], [3] and[4]).

Element 43 is a display layer followed immediately by an angularprofiling layer. The angular profiling layer might be a lenticular lensarray to provide stereopsis to the viewer, or it might be a lensletarray or any other angular profiling layer to provide autostereoscopic3D or provide different images to different angles.

Element 44 is an angled display layer, followed by a cavity with aninternal polarization clock whose ends are composed of PBS layers. Inbetween the PBS layers is a birefringent layer 45 such that differentangles of propagation result in different retardation of polarization.The shutter layer at the aperture is tuned into a desired polarizationso that only one of the round trips are allowed to exit the cavity, andthe transmitted light has traveled a desired optical path or depth. Thisis a representation of coaxial FECs with polarization clocks andsegmented gated apertures with desired gating mechanisms [2, 3].

Element 46 is a display followed by a micro-curtain layer and a QWP toact as pre-cavity optics. This allows desired profiling of the light ofthe display. The pre-cavity optics can adjust the polarization orangular distribution or other properties of the light entering thecavity. Element 47 is of a stack of layers: a display layer, a QWP, amicro-curtain layer, and an antireflection layer. This subsystem is usedin many other disclosed systems and is categorized as a display. Themicro curtain can be arbitrarily engineered, and it allows for controlof the directionality of the light and the visibility of the display.The AR layer allows for reduction of ambient or internal reflections ofthe systems that use this subcomponent. Element 48 is a sub-assemblythat includes a transparent substrate that has an AR coating and anabsorptive polarizer on one side facing the user and outside world, andanother AR coating or film and a QWP on the side that faces the displayfrom which light exits. In this disclosure, 48 is referred as a shieldlayer. Element 49 is a sub-assembly of a display with micro curtainlayer and an AR coating on top. Element 50 shows a sub-assembly thatincludes two mirrors on the top and bottom, a display at the back, andan angled PBS with LC in the middle such that the electronic signal tothe LC can change the length that the light must travel before it exitsthe cavity. In some embodiments, there might be a stack of such angledPBS-on-LC splitters such that the length of the light travel can beprogrammed or controlled in multiple steps. In some embodiments, themirror might be a QM to rotate the polarization of the light. In someembodiments, the reflectors can be curved and parabolic to give extendeddepth.

Note that certain features described below are constructed from thebasic “building block” components shown in FIG. 1 and defined above;these may be referred to as “compound” or “multi-layered” features. Suchcompound or multi-layered features may be referred to below and insubsequent figures with a name and corresponding reference numeraldesignating the feature as a whole (e.g., the semi-reflective optic(110) in FIG. 3A), and may also be referred to in this description byreference to their individual constituent (“building block”) componentsor layers (e.g., the semi-reflective optic (110) may also be referred toas a beam splitter (19) with antireflective coating (27)). Thesealternative ways of referring to the same features will be readilyapparent to and understood by those skilled in the art.

FIGS. 3A through 3D depict a set of example embodiments that representfour architectures to provide tunable depth modulation in concentricnear-head lightfield displays for first-order and higher-order FECcavity designs. FIGS. 3E through 3H are views of the embodiments ofFIGS. 3A through 3D, respectively, in which the multi-layered componentsare shown in “exploded” form. These architectures provide multiplelayers of depth and eye comfort by using longer focal lengths andincreasing the object distance to the lensing mechanism. They alsoprovide compact architectures such that the aspect ratio from the sideis not a square but rather an elongated, tall rectangle. FEC cavitieshave a set of preparation optics that can in turn have severalalternative embodiments.

FIGS. 3A and 3E each illustrate a perspective view of the tunableconcentric near-head lightfield display embodiment where active,switchable reflectors are used to terminate one end of the cavity andcan be electronically addressed to tune to the resulting level ofinduced optical depth modulation. For example, in this embodiment thelight is originated from an emissive display or array of displays (1).Then the light from the display (1) passes through a set of pre-cavityoptics (29, 27) to condition the light before going through an FEC withfixed or switchable optical elements (37) that determines and tunes theoptical depth in desired increments. The light then is reflected back bythe switchable optical elements 37 to a semi-reflective optic 110 madeof internal passive optical elements (19, 27) in the cavity, whichreflects the light back toward a 2D-curved (freeform) back reflector(111). The back reflector (111) can be made of a mirror (3) disposedover a free-form optic (4). Then the light reflects off the backreflector (111) and is passed through the semi-reflective optic andthrough a shield layer (112) made of passive elements (8, 27, or 48) onits way toward the user's eyes (not shown).

The back reflector (111) can be arbitrarily engineered. In someembodiments the back reflector has a thin layer to impact the propertiesof the light. In some embodiments this layer can be a thin glass layerwith a thin QWP lamination (10). In some embodiments, the back reflector(111) can be a flat or curved DOE (13). In some embodiments, the backreflector (111) can be a flat or curved metasurface with nanostructures.In some embodiments, the back reflector (111) can be a tunable freeformsurface.

In some embodiments, the layer stack of switchable optical elements (37)can include reflective coatings, anti-reflective coatings (27), QWPs(10), HWPs (9), or partially absorptive layers. In some embodiments, thelayer stack of switchable optical elements (37) is laminated ordeposited on back reflector (111). In some embodiments, the layer stackof switchable optical elements (37) changes the directionality of thelight in conjunction with a nano-imprint structure on the back reflector(111). In some embodiments, the layer stack of switchable opticalelements (37) is switchable in polarization, reflectivity, or absorptiveproperties via an electric signal.

The shield layer (112) functionally mitigates the nonuniformity(waviness) observed in the virtual image and decreases the ambient lightnoise received by the user. Some part of the ambient light reflectsdirectly from the shield layer, and some part of the ambient lightenters the cavity and comes back. The shield layer (112) is a stack oflayers laminated or deposited together such that the light that entersthe cavity changes polarization and is absorbed by the stack ofpolymers. In some embodiments, the shield layer stack (112), dependingon the polarization of the signal light or the image light) is tilted orbent to further decrease the ambient light and internal reflections ofthe cavity. In some embodiments, the shield layer stack (112) iscomposed of absorptive polarizers (8), QWPs (10), or arbitraryantireflection coatings (27). In some embodiments, the shield layerstack (112) has an absorptive substrate (28) to further decrease theambient reflection because the ambient light passes twice through theshield layer stack. In some embodiments, the shield layer stack (112)has a liquid crystal layer (12,13) or optically tunable layer such thatthe electric signal applied (26) to the shield layer stack (112) can beleveraged to choose the image depth that needs to exit the cavity. Insome embodiments, there is a liquid crystal layer with oscillatingpolarization on the shield layer to provide both polarizations to theoutside world.

As an extension of this mechanism, switchable reflectors with higherorder FECs provide tunable, multilevel depth modulation functionality.For every j levels (j=1:M) of switchable reflections that the LC stacklayer can support, the resulting total number of optically modulateddepth layers scales as a function of the order i, of the FEC (i=1:N):the number of optical depth layers is MN.

Notably, by using the configuration shown in FIG. 3A, the depth of thedisplay system can be less than half the focal length of the displaysystem at maximum magnification. The “depth” of the display device, inthis context, is the distance between the frontmost point of the backreflector and the frontmost point of the aperture of entire displaysystem.

The perspective views of the embodiment in FIGS. 3B and 3F illustrate acompressed cavity, which has a thinner footprint than that illustratedin FIG. 3A. Light is emitted from an emissive display (1), passesthrough pre-cavity optics (27,10, 29), is reflected by a narrow beamsplitter (117) made of elements (19, 27) inside the cavity, is reflectedby a 2D back reflector (116), and then passes through the beam splitter(117) and post-cavity optics and shield layer (118). Stray light isabsorbed by an absorptive layer (28) at the bottom of the cavity. Thiscompressed embodiment allows flattening of the effective curvature ofthe curved back reflector 116 and consequently flattens the virtualimage spatial distribution. This is achieved by making the aperturetaller in a thinner overall body, which effectively enables a largerfocal length with the largest volumetric viewable zone compared to the“uncompressed” embodiment of FIG. 3A. In this embodiment, the beamsplitter (117) has at least one segment that partially reflects thelight to the reflector (116), and the rest of the parts interact withthe light from the display (1) differently, such that the distance fromthe center height of the beam splitter (117) to the center height of theback reflector (116) can be less than one third of the height of theback reflector (116). In some embodiments, the beam splitter (117) is orhas layered on it a micro-curtain layer (29) for extra freedom in theangular profiling of the light. In the embodiment of FIG. 3B the depthof the display system can be less than half the focal length of thedisplay system at maximum magnification.

FIGS. 3C and 3G each depict a perspective view of an embodiment thatuses multiple seed (display) panels (1) to produce multiple depthlayers. The beam splitter (120) can include switchable layers(12,13,16,17) to effect higher-order reflections within the cavity, andin some light paths, the light bundles can be directed directly towardthe viewer or can be reflected by a curved back reflector (121) (e.g., amirror (3) disposed on a free-form optic (4)). Light from the bottomseed panel (1) passes through pre-cavity optics (9,10,27,29) and isreflected by beam splitter 120 directly through post-cavity optics(27,10,8) and then thorough the shield layer (122) to the viewer. Lightfrom the top seed panel (1) passes through pre-cavity optics (10,27,29)and is first reflected by beam splitter 120 toward the curved backreflector (121). The light is then reflected by the back reflector (121)and transmitted through the beam splitter (121) before passing throughpost-cavity optics (27,10,8) and shield layer (122) to the viewer.

FIG. 3D depicts a perspective view of an alternate FEC embodiment where1D-1D bent optical surfaces (22) or DOEs, holographic optical elements(HOEs), metasurfaces, or Fresnel components (14) are introduced into theFEC design as an alternative way to control the evolving wavefront ofthe light in the cavity to provide wavefront control in perpendiculardirections independently. This approach allows for lower complexity andwider manufacturing tolerances than with a single 2D optical componentwith the similar optical functionality and performance. A 1D-1Darchitecture such as this also provides a notable decrease in effectivecomponent weight, because thinner layers can be used.

In FIGS. 3D and 3G, light travels upward from the seed display panel (1)located at the bottom of the cavity, through pre-cavity optics(10,27,29) and through the beam splitter (126), after which it isreflected back downward by the first one-dimensional (1D) reflector (22)located at the top of the cavity. The light is then reflected backtoward the second 1D reflector (22), which is located at the back of thecavity and oriented perpendicular to the first. The light is thendirected through the beam splitter (126), post-cavity optics(27,10,8,27) and shield layer (128) to the viewer. The combination ofthe two reflections from perpendicular 1D reflectors acts as acombination of two cylindrical lensing components that together providethe desired 2D convergence or divergence for the wavefront.

In some embodiments the 1D-1D curved reflector is such that thereflector is physically bent in one dimension and has a surface gratingor DOE variation the perpendicular dimension to collectively act as afreeform 2D surface. The light then exits the display aperture, which iscovered by a shield layer (8, 27 or 48) from the outside world. In someembodiments, although the back reflector is 2D, a layer stack (37) canbe one dimensional, meaning it bends in one dimension. This is to allowthe users head to submerge further into the aperture hence providinglarger field of view.

In the embodiments of FIGS. 3A, 3B, 3C and 3D, the beam splitters (110,117, 120, 126) may each have an antireflection layer (27) on the sidefrom which light is to be transmitted through it. Also, in theembodiments of FIGS. 3A, 3B, 3C and 3D, the shield layers (112, 118,122, 128) can each include an absorptive polarizer (8) coating and anantireflection layer (27).

FIG. 4A is a block diagram depicting common system processing buildingblocks that can be used to render either 2D or 3D content into thedisplay system, in accordance with implementations of this disclosure.The display system is controlled by the computer and synchronization(“sync”) circuit. Any pre-existing 2D or 3D content is processed by acomputer (if necessary) and passed to the light source block. Theprocessing might be to distort the image geometrically, or it might beto mask the image for multiple panels to appear as a larger image forthe viewer after viewed through the optical system, or it might be toprovide better field of view or fit all four corners of the image intoviewer's field of view depending on viewer's location in front of thedisplay. The processing might be to provide multiple layers ofinformation at different depths. This subblock has a content engine,which executes the processing, and a depth control subblock, whichsignals the synchronization circuit. The sync block has two subblocks:one subblock is the sensor that can read an optical signal from theshown video stream on the emissive display, and the other subblock isthe control circuit that commands the switchable mirror stack to controlthe optical path and consequently the depth of the shown image. Thelight source can be any one of a number of sources, or it can be acombination of multiple sources. As noted in the block diagram, it is anemissive display, so it can be based on any image creation technology,such as OLED, LCD, LCoS, etc., and it can be 2D, or autostereoscopic 3D,or any type of emissive display. Before being directed into the cavity,the light generated by the emissive display is impacted by pre-cavityoptics to prepare the light for the rest of the system. In thesepre-cavity optics, the polarization, directionality, intensity, color,or wavefront of the light might be impacted. When the light enters thecavity, it travels one or multiple round trips using intra-cavityoptical components that are shaped geometrically and patterned withstructure to impact the wavefront of the light. The light path can bemodulated using switchable devices, and the wavefront shaped usingarbitrarily engineered optical components. The light then exits thecavity where it is impacted for optimal viewing. The light passesthrough the exit pupil toward the user. Throughout the operation, thedisplay system is synchronized with the computer that generates or playsthe content. The typical examples of components for each block are givenin the block diagram, and any arbitrary combination of these componentsmight be used.

FIG. 4B is a block diagram depicting common system processing buildingblocks used to capture and record either 2D or 3D image content from anexternal scene, in accordance with implementations of this disclosure.Light enters the system through the aperture and is impacted before itenters the cavity. A combination of intra-cavity optics and switchabledevices redirects the light along different paths within the cavity. Thelight then exits the cavity for post-cavity optical filtering, afterwhich it is recorded by one or multiple sensors and digitized to be sentto computer memory. Here, the computer directly controls the synccircuit block to program or impact the light path inside the system.Different light paths can impact the optical zoom, focal plane, andlighting of the imaging system. The sync circuit for imaging systems(FIG. 4B) has two major subblocks: the sync sensor, which can betriggered by the outside signal coming to the camera or directly by thecomputer and, in turn, itself trigger control circuits; and the controlcircuit, which can impact switchable mirrors, wavefront-impactingoptics, and imaging sensor settings. The typical examples of componentsfor each block are given in the block diagram, and any arbitrarycombination of these components might be used.

FIGS. 5A through 5K illustrate a set of embodiments, or an embodimentvariation, for displays using switchable stacks, corresponding to theembodiment of FIGS. 3A and 3E. In the embodiment in FIG. 5A, light raysare emitted by an emissive display with arbitrary pre-cavity optics suchas micro curtains, wave plates, AR coatings, etc. (hereinaftercollectively referred to by reference numeral 49), through the beamsplitter (19) with antireflection layer (27) to the switchable stack(37), after which it is reflected to the curved reflector (3,4),transmitted twice through a QWP (10) to shift polarization, and thentravels through an absorptive polarizer (8) and antireflection layer(27) to the user (51) to increase the headbox size from (52) to (53).Here, the first reflection from the BS 17 goes directly toward theshield layer and is absorbed by the absorptive polarizer so it is notallowed for it to come out to the viewer. In some embodiments, acomputer takes in 2D or 3D content (54, 55) and estimates the best-fitdepth layers corresponding to that content through an optimizationprogram that minimizes error. For example, some 3D content is providedwith a game engine with the character in the front layer, the mid-groundin the middle layer, and the background environments in an opticallydeeper rear layer. The atmospheric particles (55) shown in the game or3D environment are shown on all three layers to create a sense of depthfor the user. This is done through depth thresholding, such thatdifferent cameras in the game engine or 3D environment engine renderonly a specific range of depths, matching the optical distances that areexpected to be created by the display. In some embodiments, theprocessing software might convert 2D content—such as videos, or games,or pictures, or any 2D imagery or text—to multifocal views by usingdepth filtration techniques. In such techniques, the images first passthrough an object segmentation algorithm. Then they pass through a depthestimation algorithm, and then different objects are tagged, or binned,to desired discrete depth layers. In some embodiments, different layers(54) might be fed by completely different sources of the content or evendifferent computers. In some embodiments, the annotation on the frontlayer might be generated based on the content shown in the deeper layerssuch that the front layer is an augmented-reality-like experience fordeeper layers. In these embodiments, the deeper layers are based on amaster application run by the user's personal computer, while the frontlayers are generated as annotation layers via another application thatreads the input on the first master application and suggests orrecommends content depending on the master's application activities. Insome embodiments, the computer shows content on different layers basedon best depth estimation of 3D or 2D content and through an optimizationprogram that fits the 3D curves layers to that depth profile withminimal error.

FIG. 5B, shows an example embodiment in this switchable stack family.Here, the display (1) can emit light that then passes through acontinuous polarization rotator material (56). A polarization retardercontinuously rotates the polarization angle of the light that passesthrough it. It is a variable polarization-control layer with desiredincrements in polarization angle. In some embodiments, this layer can bemeshed or be a grid such that the polarization of each pixel or desiredsubset of pixels can be controlled. The light then passes through a beamsplitter (19) and is reflected by a monolithic birefringent reflector(57) such that different polarizations experience different opticalthicknesses and therefore travel different optical depths. Themonolithic birefringent material can be a stack of two crossedpolarizers (8) or polarization-dependent reflectors. The polarizationmodulation can vary across different pixels in one frame of the display,and it can be modulated for a given pixel over time. After reflection,it bounces off the beam splitter (19), then a curved reflector (3,4,10),and finally passes through post-cavity optics and shield layer (48) tothe user. The emitted light can be of arbitrary polarization (58).Similarly, as shown in FIG. 5C, some embodiments can operate intransmission mode and can emit light from the display (1) through anelectro-refractive or photorefractive layer (59), which can modulate thelocal or global refractive index using electrical or optical signals andthen send the light through the beam splitter (19). In some embodiments,the electro-refractive or photorefractive layer (59) can be modulated bya signal in the display content itself to change the virtual depths. Thelight experiences a round trip through a second electro-refractive layer(59) via reflection by a flat mirror (3). The beam splitter (19)redirects the light to a rear curved reflector (3,4,10), which thensends the light through post-cavity optics and shield layer (48) to theuser. In some embodiments, the electrorefractive or photorefractivematerial (59) might be replaced with an FEC with a Faraday rotatordesigned such that the light travels a polarization-dependent number ofround trips before it exits the cavity.

The embodiment shown in FIG. 5D is similar to those in FIG. 5B and FIG.5C but has a switchable stack (37) or LC layer stack (12,13) composed ofa mesh grid (60) or multiple mesh grids with the same or differentperiodicity (60), whose elements can be switched individually such thatdifferent pixels experience different depths. Grid layers can haveidentical resolutions or varying resolutions to produce different delayprofiles. Light travels from the display and pre-cavity optics (49)through the beam splitter (19) to the grid (60), which reflects thelight back to the beam splitter (19) to the curved reflector (3,4,10),and through the shield layer (48) to the user. Instead of reflectorgrids (FIG. 5D), some embodiments can emit light from a display (1)through a transmissive grid (61), shown in FIG. 5E, which may include anLC stack (12,13) to provide a parallax barrier and produce stereopsissuch that the left eye and right eye see different pixels at differentangles. The display can be any type of autostereoscopic display in thisembodiment. Light travels through the grid and beam splitter (19), whereit is reflected by a QM (31) to a curved reflector (3,4,10), andtransmitted through the shield layer (48) to the user.

In the embodiment shown in FIG. 5F, after the display emits lightthrough a lenslet array (43) or other angular profiling layer (11), thelight is collimated, and it then propagates through a stack ofswitchable diffusive/transmissive grids (62). When a grid element isturned OFF, it is transparent. When a grid element is turned ON, it actsas a screen, and the light that strikes it produces a point source atthat particular position. By varying the elements in the ON/OFFposition, the point source depth of each pixel can be changed. The lightthen travels through the beam splitter (19), to a QM (31), to a curvedreflector (3,4,10), and through the shield layer (48) to the user. Theflat mirror here is to increase the display's optical path to the curvedreflector so that a smaller curvature is required for the reflector;this allows the increase in the headbox region.

In FIG. 5G, light is emitted from the display (1), and anelectrically-controlled liquid-crystal HWP (9) can rotate thepolarization of the light. The light strikes a PBS (20). x-polarized ofthe light, when the HWP is ON, experiences a first-order reflection fromthe PBS (20) and passes directly through the shield layer (48) to theuser. When the HWP is OFF, the light is converted into y-polarizedlight, travels through the PBS (20), is reflected by a QM (31), whichrotates the polarization 90 degrees, into x-polarization. At this pointthe light cannot pass through the PBS (20) anymore, so it is reflectedby it and then by the curved reflector with QWP, which rotates thepolarization through another 90 degrees, back into y-polarization, andreflects it through the PBS (20) and then, finally, through the shieldlayer (48) to the user. This first- and second-order reflectionscorresponds to two different depth layers (54).

As shown in FIG. 5H, in the majority of embodiments, the curved mirrorcan be replaced by a half-reflective curved mirror or thin lens or thinlens group (19,4,10) that can be positioned closer to the user toincrease the field of view and the headbox. In the figure, the dottedbox (63) represents any display (1) or any FEC or other cavityarrangements, which contain multiple display elements (1),retroreflectors (18), LC layers, and beam splitters (19). Thehalf-reflective curved surface can be combined with a PBS (20),absorptive layer (8), and antireflection layer (27) to act as a compoundreflector. Here the top display and the back display have absorptivepolarizers to absorb unwanted internal reflections of other displays;the light from back display passes through the PBS (20) through thefront lens and exits the cavity. The top display emits light downward,where half of the light is transmitted through the PBS (20) and then isreflected from the surface of the bottom display with a perpendicularpolarization. It then reflects back toward the semitransparent freeformoptic and exits to the world. The light from the bottom display justgoes up and is reflected by the PBS (20) toward the outside world. Thebottom display creates length P1, the back display length P2, and thetop display length P3, such that P1<P2<P3. After the freeform optics,the viewed images would appear at three different depths that aresignificantly differently from one another. In a majority of embodimentsand sub-embodiments of FIG. 3 , the reflector can be replaced by asegmented reflector to combine images from multiple displays whiledeleting or concealing the lines between the smaller displays resultingin an optically fused, larger continuous image with larger FoV (see U.S.Pat. No. 11,196,976, hereinafter “reference [5],” and U.S. PatentApplication Publication No. 2022/0057647, hereinafter “reference [6],”both of which are incorporated herein by reference in their entirety)

FIG. 5I illustrates an embodiment in which multiple OLEDs or thinflexible displays (64) or curved displays (5,49,64) and/or thereflective mirror or QM (31) can be shifted mechanically with avibrating coil or an arbitrarily engineered actuator or actuator arrays(15) to change depth locally or globally by varying the physical paththat the light travels. In this embodiment, the PBS (20) can includeantireflection layers (27). After the light bounces off the curvedreflector (3,4,10) and through the beam splitter, it passes throughanother PBS (20) and antireflection layer (27) to the user to minimizestray reflections. In some embodiments, as shown in FIG. 5J, themultiple sets of displays and pre-cavity optics (49) can each haveplaced after them multiple switchable EORS stacks (37) with asemi-transparent curved mirror or thin lens or lens group (19,4,10) andPBS elements (20, 8, 27). Light from one display will travel through itsassociated stack and is reflected the other display's stack. Both pathswill travel through the curved semi-transparent mirror, both sides ofwhich include a QWP (10), and are fused together with a segmented orbent PBS (20) that act together as a compound reflector.

FIG. 5K depicts an embodiment with two orthogonal displays (1) each withswitchable LCD layers (12,13) and semi-reflective surface coatings. Whenboth LCs are OFF, the light from back display just passes through PBSand exits to the outside world, and the light from bottom displaytravels up, reflects from the PBS, strikes the surface of the backdisplay that is semi-reflective, experiences polarization rotation dueto the QWP on top of back display, passes through PBS, and then exits tooutside world. When the LC on the back display is ON, the light hits thePBS, goes down and up, but it still cannot exit the PBS because there isno QWP on bottom display to rotate its polarization appropriately. Thelight then has to go back and hit the surface of the back display againwhere, because of QWP, it experiences 90-degree polarization rotationand now can pass through the PBS. These three light trajectories followoptical paths P1, P2, and P3, such that P1<P2<P3. The result to theviewer is three layers of depth. This embodiment does not have anylensing or curved optics, so it allows the viewer to see the depth withinfinitely large headbox. This is appropriate for, but not limited to,in-vehicle or dashboard applications, which is discussed further below.

FIGS. 6A through 6K illustrate a set of embodiments for displays with acompressed cavity, corresponding to the embodiment of FIGS. 3B and 3F.Generally, surfaces can be macroformed such that their shape isarbitrarily engineered in one or two dimensions. The macroforming can bestatic or time-varying, such that mechanical waves travel across thesurface and shape the surface spatially and temporally. The macroformingcan be modulated in time with mechanical or with other actuators usingultrasound or acoustic waves, or it can be modulated electronically. Asshown in FIG. 6A, a compressed cavity brings the curved reflectoreffectively closer to the user and increases the headbox from a smallsize (52) to a large size (53), and it increases the field of viewcompared to an extended cavity. The object distance (the opticaldistance from the display to the curved reflector), however, remainslong. Light of arbitrary polarization (58) travels from a display oranother cavity through pre-cavity optics (47), where it is reflected bya beam splitter and antireflection layer (19,27) to a curved reflector(freeform optic and mirror) (3,4) and passes through a layer stack,including an antireflection coating (27), and shield layer (48), to theuser (51). FIG. 6B depicts another example embodiment with a doublereflector forming a wedge-type structure. The light from the display (1)reaches the viewer, horizontally in the figure, only after multiplebounces, each of which increase the optical depth before striking thecurved reflector with QWP (3,4,10), which serves to rotate thepolarization 90 degrees so that it can pass through the tilted frontreflector. The physical depth is shorter than the optical path lengthbecause the angle of the tilted reflector is less than 45 degreesrelative to the vertical. Two baffles (48) act as shield layers andprevent the user from seeing the displays directly. The architecture isdesigned such that the light from the display comes down, strikes thePBS, but it is not initially allowed to pass to the outside world. Thenthe light travels toward the interior vertical, flat reflector and isbounced back toward the PBS; the PBS still is cross-polarized, and thelight now travels toward the curved reflector. The vertical reflector atits center height is 100% transparent, so the light passes through itand hits the curved reflector with QWP, which makes the polarizationparallel to pass angle of the PBS. This light now passes through the PBSand exits to the outside world. In some embodiments, the tilted layermight be a reflective surface that changes reflectivity with incidentangle.

Instead of flat, static reflectors, the embodiment in FIG. 6C emitslight from a display (1) and includes an anamorphic macroformed surface(65) that is excited by mechanical (e.g., ultrasonic or acoustic) wavesat desired frequencies and amplitudes to produce reflection andtransmission. The image is rastering in sync with the waves traveling onthe reflector. The material can be made of polymer-based materials likePMMA, thin glass, and combinations of glass and polymer-based materials.The polymer-based material might have a semi-reflective coating or actas a substrate for a thinner layer of glass. The display israster-scanned or has a shadow mask, and it is synchronized with thesurface waves on the anamorphic layer to deflect light rays at specificpositions along different distances. The image shown can bepre-distorted to compensate for distortions induced by the anamorphicsurface at desired times. Light from the display (1) is x-polarized andis reflected by the anamorphic beam splitter. The curved reflectorincludes a QBQ layer to rotate the polarization into y-polarized lightsuch that it can pass through the anamorphic beam splitter. Light fromthe display panel pixel t1 travels a distance p1, and likewise forpixel-distance pairs t2-p2 and t3-p3. These light rays strike the curvedreflector (3,4,10) and pass through a shield layer (48) to the user. Theshape of the reflector (65) is such that the effective angle it makeswith the horizontal is greater than 45 degrees, but the positions wherethe waves strike are shallower so that they exit the cavityhorizontally. The cavity's physical depth is compressed whilemaintaining a wide field of view, as illustrated by the wider separationbetween the light rays across the shield layer (48) compared to theirseparation at the display panel (1).

In some embodiments, the synchronization between the light emitted fromthe display panel and the motion of the anamorphic surface can redirectindividual pixels, t1, t2, and t3, to travel different lengths or todifferent positions relative to the user's eyes to create stereopsis orto adjust the monocular depth. In some embodiments, angular profilinglayers can help redirect these light rays. The timing of the display andanamorphic reflector is controlled in such a way that the curvedreflector sees a vertical reflection of the display that can be talleror shorter than the physical height of the display. This effect can beachieved both with changing the timing or with increasing the amplitudeand frequency of the macroforming waves on the surface of the anamorphicreflector.

Similarly, the embodiment in FIG. 6D generalizes that in FIG. 6C andincludes multiple anamorphic surfaces (65) that act together as awaveguide or image guide. The surfaces are modulated with mechanicalwaves such that the surfaces shapes are complimentary. Two tilteddisplays (1) couple light into the waveguide at such an angle that thelight that exits the waveguide toward the curved reflector hashorizontal chief rays after two or multiple reflections withcompensating steep and shallow angles. In some embodiments, thesewaveguides are polarization-dependent and include shield layers andreflective coatings (66) at different regions of the waveguide toincrease the efficiency. The top and bottom portions of the surfaces canbe fully reflective to increase efficiency. The light can be ofarbitrary polarization (58).

The embodiment in FIG. 6E includes tessellating structures known asorthogonal field evolving cavities (OFEC) (see reference [5]). A display(1) emits light, which immediately passes through a lenslet orlenticular lenslet or pinhole array (67), or other angular profilingelement (11), which tilts light from different pixels into different,specified directions. Vertical mirrors (3) guide the different rays to abeam splitter (19,27), which redirects different cones of light todifferent parts of the rear curved reflector (3,4,10). The light raysthen travel through the beam splitter (19, 27) and shield layer (48) tothe user, who views different cone bundles coming from differentheights. One cone of rays produces image I1, a second cone I2, and athird cone I3. Each of these sub-images is fused together to create, orvertically tile or tesselate, a wider vertical field of view. Here, theimages of each subset of pixels represent a certain tile or segment ofthe total image, so the seed image should be interlaced with differentsegments that are shown on the higher-resolution, narrow panel at thecore of OFEC (see reference [5]). In some embodiments, the OFEC may haveswitchable, polarization-based mirrors that are time-synchronized.Examples of the OFEC and how to program it are described in reference[5].

In FIG. 6F, a single anamorphic reflector can be used withlarge-amplitude surface modulation. It is fully reflective at the edges(68) to guide the display light efficiently to a semi-reflective region(69). The light then reflects from a curved reflector (3,4,10) to theuser. The vertical orientation of the displays increases the compressionof the cavity. The curved reflector can include a QWP layer to rotatethe polarization 90 degrees for polarization-dependent reflections.Instead of a modulated anamorphic reflector, the example embodiment inFIG. 6G uses a curved PBS (70) before the curved reflector (3,4,10) soas to bring the curved reflector effectively closer to the user andincrease the field of view. The beam splitter (19) can be curved ineither one or two dimensions, but the impact that this curvature has onthe light should be compensated for or considered in the design of thecomplementary back reflector and seed image, such that the net effect isthe desired virtual image. Thus, the image on the display ispre-distorted so as to computationally compensate for any distortionsinduced by the beam splitter. The back reflector also exhibits verticalfreeforming (4) to optically compensate for the beam splitter's shape.The light emitted by the display is x-polarized and is reflected by thecurved PBS. The curved back reflector includes a QWP layer to rotate thepolarization 90 degrees such that it can pass through the PBS to theuser.

As shown in FIG. 6H, the emissive display of the majority of theseembodiments can itself be replaced by an arbitrarily engineered FEC (71)with multiple displays to generate a plurality of depth layers or toincrease brightness. The dotted box can represent any such cavity.Vertical displays do not reduce the compression of the embodiment, andthe embodiment functions in the same way as others. x-polarized light isemitted by the FEC (71), is reflected by the PBS (20), then reflected bythe curved back reflector (3,4), which has a QWP (10) to rotate thepolarization. The light is now y-polarized, and travels through the PBS(20) and shield layer (48).

Some embodiments, such as that shown in FIG. 6I, use rotatingone-dimensional mirrors (72) to create two-dimensional lensing with atunable or rastering focal length. In FIG. 6I, an emissive display (1)or a projector emits x-polarized light, which is reflected by a PBS (20)through a QWP to produce circularly polarized light. The light isreflected by a one-dimensional rotating mirror (72) back through the QWP(10), which results in y-polarized light that can now pass through thePBS (20). The light then passes through another QWP (10) again producingcircularly polarized light, which is then reflected by a secondone-dimensional rotating mirror (72), oriented perpendicular to thefirst. The reflected light again passes through the QWP (10) and isconverted into x-polarized light that is finally reflected by the PBS(20) to the user. Such embodiments are most suited for micro projectionor a component for headset-based systems.

FIG. 6J illustrates an embodiment in which x-polarized light thattravels upward from the emissive display with pre-cavity optics (49)through a PBS (20) steeply tilted at an angle greater than 45 degrees.The light then strikes a titled QM (31), which reflects y-polarizedlight at a titled angle. The light is reflected by the PBS (20), thenreflected by the curved reflector (3,4) and QWP (10), which rotates thepolarized back into the x-polarized orientation. The light istransmitted through the PBS (20) and through the shield layer (48). Insome embodiments, the emissive display at the bottom might have an OFECto tesselate larger vertical fields of view. In some embodiments, themirror at the top might be a 1D or 2D convex mirror to adjust theoptical distance and engineer the desired vertical field of view.

FIG. 6K depicts a display in which pre-cavity optics (47) emitx-polarized light. The light travels upward through a tilted beamsplitter (19,27) and is reflected by an EO reflector (33), which can betilted at different angles, or a stack of EO reflectors with differentangles that turn reflective and transparent at different times. The netresult produces light rays that are reflected at different angles atdifferent time intervals. This embodiment therefore can raster, from anarrow display, a larger vertical reflection for the curved backreflector. All the light rays are reflected by the curved back reflector(3,4,10) and then propagate through the beam splitter (19,27) and shieldlayer (48). In the figure, the most steeply tilted position of the EOreflector (33) results in light path t3. The moderately steep positionresults in light path t2. The shallowest position results in light patht1. The combination of the titled EO reflector (33) and steeply tiltedbeam splitter (19,27) allow for a thinner overall footprint whilemaintaining a larger vertical field of view.

FIGS. 7A through 7F illustrate a set of embodiments for multi-focal andfractional lightfield displays with multiple seed display panels,corresponding to the embodiment of FIGS. 3C and 3G. In FIG. 7A, lightwith arbitrary polarization (58) travels both up and down from emissivedisplays with pre-cavity optics (46,47). Light from the bottom displaylayer is reflected by a beam splitter and anti-reflection coating(19,27) to the user, and light from the top display is first reflectedto the back curved reflector (3,4) and then exits to the outside world.Both sets of light bundles travel through a stack of layers (27,10,8,27)before reaching the user (51). The result is multiple depth layers (54)seen by the user. In some embodiments, the lower display can be coveredwith absorptive micro-curtain to block direct line of sight light.

FIG. 7B shows a similar embodiment that replaces the center beamsplitter with a PBS (20) sandwiched between switchable LCD layers(12,13) that themselves switch between two modes. Two displays (1) cangenerate four layers of depth in total. When the LCD layers are ON (12),they leave unchanged the x-polarized light is emitted from both of thedisplays (1). The light passes through a QBQ (30) stack laminated on topof the display; the light rays are then reflected by the PBS (20). Lightfrom the top display is then reflected by the back reflector (3,4), andthe QWP (10), which results in y-polarized light that travels throughthe PBS (20) to the user and corresponds to a distance P1. The lightfrom the bottom display is reflected directly to the user andcorresponds to a distance P2.

When the LCD layers are OFF (13), the x-polarized light from top display(1) again passes through a QBQ (30) and is rotated by the top LCD layer(13) into y-polarized light. It passes through the PBS (20) and throughthe bottom LCD layer (13), such that it leaves as x-polarized lightagain. It strikes the QBQ (30) laminated on the bottom display, whichrotates the polarization into y-polarization and reflects it back up;the light is now reflected by the PBS (20) to the user and correspondsto a distance P3. When the LCD layers are OFF (13), the x-polarizedlight from bottom display (1) and QBQ (30) travel through theLCD-PBS-LCD layer (13,20,13), is reflected by the QBQ (30) laminated tothe top display, which rotates the polarization and reflects the lightback down. The light is then reflected by the LCD-PBS-LCD layer(13,20,13) to the curved reflector and QWP (3,4,10), which rotates thepolarization again, such that it passes through the LCD-PBS-LCD layer(13,20,13); it exits the cavity and corresponds to a distance P4. Intotal, four possible depths are produced.

Similarly, the embodiment in FIG. 7C uses a liquid-crystal layer andbeam splitter in a different orientation relative to the display andmirrors to produce different depth layers. When the LCD is ON (12),x-polarized light is reflected by the PBS (20) to the curved reflectorwith QWP (3,4,10), rotated into y-polarization, and travels back throughthe PBS (20) and through the shield layer (48). When the LCD is OFF(13), y-polarized light travels through the PBS initially. There is a QM(31) reflector at the bottom which transforms the light into x-polarizedlight, which is then reflected by the PBS (20). These two optical pathsresults in two depth layers seen by the user.

In FIG. 7D, the curved reflector (3,4) is half reflective. In thisembodiment, all the displayed depths are curved and have largedistances. The light from all of the display panels (1) on the top,bottom, and back (or left) of the cavity interact with it and thereforecreate longer distance virtual images. The top display has a reflectivelayer to increase the optical path. Light rays from the left and bottomdisplay panels are reflected by this layer before striking the curvedreflector. Micro curtains on the top and bottom displays will preventunwanted light from entering the user's eye. Three representative lightpaths indicate relative distances. y-polarized light (P1) from the leftdisplay panel (1) travels directly through the curved reflector (3,4),is reflected by PBS (20) upward, and then is reflected by thesemi-reflector on the top display. It then travels down to the PBS andbecause it is still cross-polarized, its travels back to the curved QBQat the back, which changes the polarization and directs it through thePBS and to the outside world. x-polarized light (P2) from the top panelis first reflected by the PBS (20) and then reflected by the curved QBQlayer to rotate the polarization 90 degrees into y-polarization, whichthen passes through the PBS (20) and shield layer (48). y-polarizedlight (P3) from the bottom display panel (1) first passes through thePBS (20), then is reflects from the coating on the top display panel,and then traces the path of P2. In this example embodiment, thedistances are ordered such that P1<P2<P3, and the result is three layersof depth for the user.

The embodiment in FIG. 7E includes, in addition to a seed display panel(1), a projector or projector array display (74). The projected light isy-polarized and strikes a polarization-dependent diffuser (73), whichthen acts like a transparent display layer. The diffuser layer can bemonolithic or a grid with individual switchable grid elements. The lightis reflected by the beam splitter (19), to the curved reflector (3,4),and through a shield layer (48). Light from the flat display panel (1)is reflected by the beam splitter and then by the curved reflector(3,4,10), which rotates the light into y-polarization for transmissionthrough the beam splitter. The projector array at the bottom can besynchronized with the image projected from the top displaycomputationally such that autostereopsis is provided, or such that itcreates higher dynamic range in the image, or such that it provides afractional lightfield such that luminosity effects such as sparkle orshimmer in the scene can be represented or amplified, or such thatdifferent images are seen from different angles.

The embodiment in FIG. 7F is an example of an X-shaped architecture withmultiple seed displays (1) and LC layers (12,13). Light from the toplayer is polarized perpendicular to that of the bottom layer. The twoPBS (20) layers are oriented such that they reflect and transmitopposite polarizations. In the ON mode, light travels from each display(1) through the closer PBS layer (20). Each is reflected by the curvedQM reflector at the back, which rotates the polarization such that thereflected light passes through the related PBS (20) layer and thenthrough the shield layer (48). In the OFF mode, the polarization of thelight from the displays (1) are first rotated by 90 degrees and aresimply reflected by the first PBS reflectors (20) through the shieldlayer (48). In some embodiments, optical fusion mechanisms such asinvisible bends and computational masking might be used to fuse theimages from different segments with no bezel line or seams in the middle(see reference [6]).

FIGS. 8A through 8P illustrate a set of embodiments for displays withmultiple one-dimensional elements to mimic two-dimensional lensing orimpact the light (the 1D-1D architecture), corresponding to theembodiment of FIG. 3D. The elements can be macroformed in one dimensionand uniform in another dimension. They can also be created in a hybrid1D-1D manner, in which the element is macroformed in one dimension andpossesses structure variation in the other direction. This structure caninclude a 1D metasurface layer or a diffractive grating or aFresnel-lens-like structure. For example, the embodiment in FIG. 8Aincludes two one-dimensional geometrically curved surfaces withcurvatures in perpendicular orientations. The result embodiment focusesin two dimensions and approximates a 2D curved surface. Light ofarbitrary polarization (58) travels up through some pre-cavity optics(46), through the beam splitter layer (19,27), and then to the first 1Dbend (22). It is then reflected by the beam splitter layer (19,27)toward the second 1D bend (22), which is oriented perpendicular to thefirst. The light then travels through the beam splitter layer (19,27),through post-cavity optics layers (27,10,8,27), and finally to the user(51). The design can increase headbox from (52) to (53) because itincreases the object distance while lowering the curvature of the curvedoptics. Similarly, the embodiment in FIG. 8B includes 1D curved displays(5), curved mirrors (22), and curved beam splitters (22). The geometriescan be adjusted relative to absorber (28) and shield/post-cavity layers(48). Light of arbitrary polarization (58) is emitted from a curvedemissive display (5) (which can be OLED or POLED in some embodiments),reflected by a 1D curved beam splitter (22), reflected by a 1D curvedreflector (22), and then transmitted through post-cavity optics (48). Anabsorptive layer (28) removes the stray light.

In the embodiment in FIG. 8C, a curved display (5) emits light ofarbitrary polarization (58), which is reflected by a curved beamsplitter (70) to a 1D curved reflector, oriented perpendicular to thecurvature of the display. The light rebounds through the curved beamsplitter (70) and through the shield layer (48). The curvatures aredesigned such that together they emulate a single 2D curved reflector.

As shown in FIG. 8D, light can be emitted from a display (1) through apolarizing 1D curved beam splitter (70) and through a 1D curvedhalf-reflector (22), all in a coaxial manner. Polarizing layers changethe polarization of the light as it makes round trips through thecavity. Circularly polarized light is emitted by the display (1),converted into y-polarized light by a QWP layer on the curved halfreflector (70), reflected by the second curved reflector (22), orientedperpendicular to the half-reflector. After a second reflection by thehalf-reflector, the light is rotated into x-polarized light, whichallows it to be transmitted through the 1D curved PBS reflector (22)toward the outside world.

In the embodiment in FIG. 8E, the one-dimensional layer can be curved,i.e., possess geometric structure, in one direction and have surfacestructure in the perpendicular direction (75). This structure can be alensing or diffractive structure and can include, for example, a DOE(14) or a Fresnel grating or a metasurface. In this embodiment, light isemitted from two display panels (1), which have reflective coatings, andtravels to the 1D-1D hybrid structure (75) through the post-cavityoptics (48). Similarly, as shown in FIG. 8F, 1D-1D structures can bothbe Fresnel diffractive structures. Light travels from the display panel(1), to two 1D surfaces (76), each oriented perpendicular to the other,and through the post-cavity optics (48).

The embodiment in FIG. 8G, includes a curved display (5) and QWP with atwo-dimensional curved mirror (4) to guide round trips for the light.This embodiment can also have an extra freeform layer (77), which can bea Fresnel or diffractive layer, or it can be a metasurface. This latterfreeform layer compensates the geometric curvature of the layer suchthat the net result is effectively an optically flat surface. Forexample, the concave 2D PBS layer that is facing the user has ametasurface or diffractive optic on top of it that has an optical poweropposite the convexity, making it optically natural or flat uponreflection or transmission. This allows further thinning of the system,bringing the user's face increasingly closer to the curvature, andproducing a larger field of view. The emitted light is circularlypolarized, converted into y-polarized light by the center element (4),reflected by the freeform surface or metasurface (77), converted intox-polarized light upon a second reflection (4), and passed through thefreeform surface or metasurface (77) to the user.

FIG. 8H illustrates an embodiment with a flexible emissive display (5).The display can be an OLED or POLED display or any flexible emissivedisplay, and this display surface is modulated with mechanical waves ofvarying frequencies and amplitudes. The 1D curved display sends lightthrough a hybrid 1D-1D structure (78) through a PBS (20).

In some embodiments, the 1D-1D structures are anamorphic and can bemodulated with mechanical vibrations with varying frequencies andamplitudes. They can be modulated in the same way as, and therefore besynchronized with, the display modulation. The modulations will adjustthe physical depth of the display and directionality of the light acrossthe image. For example, the embodiment in FIG. 8I uses two anamorphic 1Dsurfaces, oriented perpendicular to each other, and modulated withsurface waves (79). They reflect light from a curved reflector with QWP(3,4,10), which changes the polarization and allows for transmissionthrough the post-cavity optics (48). x-polarized is reflected by theanamorphic layers, converted into y-polarized light upon reflection by acurved reflector (3,4,10), and propagates through the anamorphic layerand shield layer (48).

Similarly, in FIG. 8J, light of arbitrary polarization (58) travelsthrough a flat beam splitter (19), reflects from two 1D-1D anamorphicsurfaces modulated with surface waves (79) in perpendicularorientations, and then propagates through post-cavity optics (48) to theuser. This embodiment generates a desired autostereoscopic and monoculardepth profile. In some embodiments, this profile may change based on aninput from a head tracking or eye tracking device.

In the embodiment in FIG. 8K, the display (1) and anamorphic surfaces(80, 81) can be arranged in a coaxial configuration in transmission modewith polarization-dependent coatings or surfaces. The display caninclude a moving shadow mask, synchronized to the anamorphic surfaces,to remove unwanted stray light and undesired artifacts. Circularlypolarized light passes through the first anamorphic layer; the secondlayer reflects the light and converts it with a QWP layer intoy-polarized light, which is reflected again by the first anamorphiclayer. It is finally converted into x-polarized light and exits thecavity.

In the embodiment in FIG. 8L, the display is curved (5) in only onedimension and emits light through a hybrid 1D-1D element (78). Thiselement is geometrically curved in the same direction as the display,but in the perpendicular direction it has a Fresnel grating ormetasurface or diffractive optical structure such that the compositionappears as a 2D surface to the display light that is reflected back fromthe front PBS layer. The outer PBS layer also possesses a freeformmetasurface or diffractive element (77). The compound structure isdesigned to mimic a flattened surface without sacrificing field of view,similar to the embodiment in FIG. 8G. The light travels back to thehybrid 1D-1D structure and is transmitted to the outside world. The netresult is an extremely thin virtual display (thinner than FIG. 8G) orfractional light field display or a multi-focal display that curves infront of the user and has only 1D geometrical curvature. In someembodiments, the display might be covered by a flexible LC layer toswitch the polarization of the light and consequently create multiplelayers of depth.

Instead of waveguiding along the structure, some embodiments, such asthat illustrated in FIG. 8M, can include a curved display (5) withsegmented one-dimensional curved surfaces. The segments areraster-scanned (turned reflective, absorptive, and transmissive)sequentially to guide light in a non-coaxial manner. LC layers with PBSelements can turn gates/segments ON (fully reflective) and OFF (fullytransparent) or absorptive to manage the unwanted reflections or lightleakage (82,83). Light is guided along preferred paths to increaseoptical throughput efficiency. A pixel can experience one round trip(t1) or multiple round trips (t2) before is exits the cavity. In someembodiments, these layers can be one-dimensional Fresnel structures andperpendicular geometric half reflectors (hybrid 1D-1D half reflector).

FIG. 8N illustrates an embodiment in which two 1D-1D pairs are orientedsuch that light is reflected by them twice. The display panel emitslight (1), which is y-polarized, through the polarized curved halfreflectors (70). This is done in two segments, top segment and bottomsegment. In some embodiments, more segments might be used. The lightbounces back from the shield layer with rotated polarization afterreflection from the post-cavity optics (27,20,8,27). Then it reflectsvertically by the polarized curved half reflectors (70) to 1D curvedreflectors (22), which have perpendicular orientations. They change thepolarization (31) and reflect the light back down to the curved halfreflectors (70). The light is reflected through the post-cavity optics(27,20,8,27) to the outside world. The top and bottom 1D reflectors canbe macroformed or moved by an actuator (15) to control the depth.Polarization optics allows for the light to become x-polarized andreflected by the curved beam splitters and through the post-cavityoptics. The double reflection from the curved half-reflectors in themiddle allow for a smaller curvature of those reflectors andconsequently increased headbox.

In the embodiment in FIG. 8O, the display (1) is vertical and emitslight of arbitrary polarization (58) to the left, where it is reflectedby a one-dimensional mirror (22) into a light pipe, one side of which iscurved (22) in an orientation perpendicular to the first mirror. Thecurvature of the first mirror is adjusted to compensate for the varyingdistances traveled by light emitted from different parts of the display.The light then travels through a piece of glass or a prismatic grating(84) or a film with angle dependent reflectivity to the user (51).

Finally, the embodiment in FIG. 8P depicts two displays that guide thelight rays between two curved surfaces. The curved surfaces can be x-and y-microformed surfaces (80, 81), or they can be macroformedsurfaces, or they can be segmented, or they can be a combination ofthese elements such that the light exits the center region and travelsto the user (51) after two or multiple reflections between the backsurface (on the left) and front surface (on the right, closer to theuser's face).

The embodiments in FIGS. 5A through 5K increase headbox space by havingthe light be doubly reflected within the cavity to fold the objectdistance on itself. FIG. 9A demonstrates a tight headbox as the light isreflected by one curved reflector. The eye distance is very short, andthe user must remain fixed in a small region of space in front of thedisplay system. In contrast, in FIG. 9B, multiple reflections by thedisplay systems in FIGS. 3A through 3D with curved reflectors extend theeye distance significantly (e.g., to about 50 cm) while keeping the samemagnification factor as in FIG. 9A. The headbox space is longer for morerelaxed viewing experiences.

Further analysis is shown in FIGS. 10A and 10B. FIG. 10A and FIG. 10Bare, respectively, perspective and side views of ray diagrams for 1D-1Dcavities. Light is emitted from a display and pre-cavity optics (46)through a beam splitter layer (19,27), and 1D bends (22) are located onthe top and back of the display system. The point spread function of anexample 1D-1D cavity is approximately symmetric within the viewable zonewith minimal aberration for the user.

FIGS. 11A through 11C illustrate schematically the manufacturing of somesubsampled Fresnel lens diffractive structures. FIG. 11A is a schematicview of such an element in single-pass transmission mode. FIG. 11B addsa reflective layer to the substrate in refractive mode, such that thelight passes through the structure twice. FIG. 11C illustrates areflective coating on top of the diffractive structure. Such diffractive1D structures can be implemented with a continuous phase profile or asubsampled one.

Additional embodiments are shown in FIGS. 12A through 12D. Thetechniques introduced above here can be implemented in portableapplications, including headsets, displays in automated cars, andhandheld devices. In headset devices, the display (1) emits light raysthat are reflected by the cavity's beams splitter surface (19,27), andthen by a single monolithic 2D bend (22). The light travels through thepost-cavity optics and shield layer (10,8,27) to the user to provide anextended head zone. Here, unlike in other headsets, the field of view(eyebox) of the left eye overlaps with that of the right eye, and theviews are separated from each eye via polarization. This allows muchbetter picture accuracy and reduces the nose blockage area present forheadsets with two separate eye channels that come from separatedisplays. In an alternate embodiment, the display emits light, which isreflected by the beam splitter surface (19,27), then by a mirror andfreeform optics (3,4), and then directed through post-cavity optics andshield layer (10,8,27) to the user. An absorptive layer (28) removesstray light. Similarly, the display can emit light, which firstpropagates through some pre-cavity optics (27,10,29), and is thenreflected by the beam splitter layer (19,27), then a 1D bend (22), thenthrough post-cavity optics and shield layer (10,8,27).

In FIGS. 12A and 12B, different polarizations of light can reachdifferent eyes, so as to provide both monocular depth cues as well asstereopsis, with no need for adjustment for the interpupillary distanceof the user. The polarization is switched by an LC layer on top of thehigher-frame-rate display such that frames are sent to the left eye andright eye alternatively. In both figures, the emissive display might bearbitrarily engineered. It might be curved, autostereoscopic,macroformed, or have an FEC or an OFEC on it or around it. Thedifference between FIGS. 12A and 12B is that in FIG. 12A, the light fromthe emissive display travels to the PBS or beam splitter and the to acurved reflector, and it is gated based on the layers in front of eacheye so that only one monocular depth is present. However, in FIG. 12B,the display is at the bottom, very much like the embodiment FIG. 3A, andthere is a switchable mirror stack on top that not only increases theeyebox, but also provides multiple monocular depth layers on top of theviewed stereopsis. This is accomplished by polarization-gating with thefront layers close to the eye and generating the entire lightfield witha large binocular overlap region.

All the embodiments illustrated in FIGS. 3A through 7F can also provideleft-eye/right-eye images in a headset format by using an alternatingpolarization and by gating the polarization per eye with polarizationelements (10,8,27), as indicated in FIGS. 12A and 12B. In someembodiments, the polarization may not be alternating in time at all butmight be provided by two displays that are inserting the light inperpendicular polarizations onto a beam splitter that is then placed asthe input emissive display in the enclosure, similar to the enclosure(71) in FIG. 6H. This allows all the layers to be passive, so there isno need for temporal switching if desired. In FIG. 12C, multiple gatesare controlled by a head-tracking or eye-tracking camera (85) to shiftthe x- and y-polarizations across the viewable zone. An example of thisimaging is shown in FIG. 12D. Here the left eye and the right eye seeslightly different images, and the user experiences parallax andtherefore stereopsis. The size of these vertical segments may varydepending on the desired headbox. These vertical segments areEO-shutters (32). Here, the shutters switch in sync with theleft-eye/right-eye frames shown by the display, and this may be donedependent on the interpupillary distance of the eyes of the user. Withthis mechanism, all the embodiments in FIGS. 3A through 7F can alsoprovide left-eye/right-eye images to provide stereopsis with multiplemonocular depths.

FIG. 13A shows an example embodiment as used in an automobile, or anyother type of vehicle, for entertainment. In the interior 86 of thevehicle the display system can be folded up into the celling of thevehicle or cabin. A mechanical support (87) for the display system canbe a folding arm that extends telescopically or can move up and downsuch that the display system (88) is moved to a comfortable region forthe viewer, who is the passenger (89) in this example.

FIG. 13B shows the application of the above-disclosed techniques in aportable device like a smartwatch (90) that can produce differentcontent layers (91), such that the layers appear deeper than thephysical aperture (90) of the watch, or such that the images seem tohover above (91) the physical aperture, all due to combination ofmonocular and binocular depth mechanisms provided by the device. Thesetechniques may be used to create a 3D image or multi-depth perception ofthe mechanical hands of a classic watch or to create a multi-depth userinterface (92) for taking a call or interacting with a smartwatch inarbitrary applications. Element (93) is the watch body, element (94) isthe driving board, and element (95) is an emissive display. In someembodiments, the display might be macroformed; in some embodiments, thedisplay may have a functional coating to increase the light efficiencyof the optical layers that are deposited on the display. Elements (96)and (101) are transducer arrays for 1D macroforming of the QBQ layer,and elements (97) and (99) are the transducer arrays for 1D macroformingthe PBS layer in a direction perpendicular to the deeper QBQ layer. Thetransducers can be, for example, mechanical transducers such as piezotransducers, magnetic coil arrays or capacitive transducers, or acombination thereof. There is a buffer PMMA or transparent elasticpolymer layer between the QBQ and PBS. Element (98) is the protectivedurable touch glass covering the system. Element (100) is a functionalbutton for interfacing with the watch or smartwatch, which can be usedto modulate the transducer arrays (96, 97, 99, 100) or electro-opticlayers for programmable/tunable depths of the displayed images. The sameor similar architecture can be used in smartphones, tablets, TVs, or anyother display in any application. For smaller devices, this approach ismore appropriate because the macroformed layers experience less lossover shorter distances.

FIG. 13C shows the implication of techniques introduced here for in-cardashboard applications. Here, element (102) is the car odometer ordigital interface layer. Elements (90) are the virtual image layers thatare sunken into the display system, away from the driver or operator ofthe vehicle. These images appear to the driver to be located at deeperdepth layers, beyond the physical location of the display. In someembodiments, the disclosed methods can be used to bring two or multiplelayers of depth into a tablet interface inside the vehicle such that theinteraction buttons appear to be popping out of, or sunken into, thetouch screen. In some embodiments, the car's odometer may appear closerthan the map, or there might be a multi-layer interface shown in theinstrument cluster. In some embodiments, the depths of layers might besignificantly different such that the close layers are a few centimetersaway from the user, but the deeper layers are optically a few metersaway. This disparity reduces the driver's eye fatigue or eye adjustmentswhile alternating looking at the road and then at the instrumentcluster.

All the displays, architectures, and systems may be madesemi-transparent by adjusting the reflectivity of the curved backreflector in the disclosed architectures or by projecting the output ofthe display aperture onto the windshield. FECs of the multilayer displaytypes (42) or (50) might be bent behind the tablet or be inserted at thefront of the dashboard to conceal the size of the device or to allowfurther depth without adding curved or freeform elements. In someembodiments, a retroreflective layer might be used or even depositedonto the surface of the emissive display to make the images appear as ifthey are popping out of the aperture instead of sinking into it. In allembodiments, the optical distance from the freeform or lensing elementsmight be longer than the focal length so that the image appears to behovering in front of the aperture as opposed to sinking into it. Inautomotive applications, instrument clusters with such hovering orprotruding images might be used for a touchless interface with thevehicle.

FIG. 14 illustrates a process associated with the techniques introducedhere, to generate 3D images in a display system. At step 141, theprocess emits light from one or more displays in the display system. Atstep 142, the process dynamically controls the path length traveled bythe light emitted from at least one display within the display system,by directing the light with a plurality of reflective surfaces withinthe display system, so that light rays corresponding to differentvirtual images travel paths of different lengths within the displaysystem, so as to form a plurality of virtual images that appear to aviewer concurrently at a plurality of different optical depths. It willbe recognized that a process similar to that shown in FIG. 14 can beexecuted in a camera or other image sensor without step 141, to capture3D images of a scene.

Any of the embodiments described above, including segmented displays,can be worn as a headset, as shown in FIG. 15A and FIG. 15B. The headset(103) can be used for both occlusive VR applications, as well astransparent, or see-through, augmented reality (AR) applications. Theheadset provides both monocular and stereoscopic depth, and it has acontinuous aperture (104) without separation for each eye. Thecontinuous aperture increases binocular overlap and eliminates noseblockage. Further, it does not require interpupillary adjustments. Theheadset (103) can have a strap (105), such as an elastic strap, to beworn around the viewer's head, and comfort-fitting protection (106) canbe added to reduce fatigue. The strap can be adjustable. In particular,embodiments using the 1D1D mechanisms described in FIG. 8 , especiallyin FIG. 8K, can be implemented here to reduce the thickness. Outwardfacing cameras (107) can be added, as illustrated, for spatiallocalization and mapping features.

In some embodiments, as shown in FIG. 15C, the user (51) can wear aheadphone and microphone (108) that interface with the headset or thatcommunicate wirelessly with other users. In some embodiments, theheadset can have eye-tracking cameras and/or gesture sensors to enablethe user to manipulate the virtual objects (109) or virtual depths (54).Other sensors, such as gyroscopes or accelerometers, can interface withthe headset (103) to infer user motion and position.

What is claimed is:
 1. A display system comprising: a display to emit ortransmit light; and an optical subsystem, optically coupled to thedisplay, and configured to provide a single continuous aperture that hasa plurality of polarization-dependent segments at different locationsacross a field of view of a viewer, such that a left eye of the viewerand a right eye of the viewer each see a different plurality of virtualimages at different depths to produce a stereoscopic and monocular imagein a continuous viewable spatial region for both eyes.
 2. The displaysystem of claim 1, such that a left eye of the viewer and a right eye ofthe viewer each see a different plurality of virtual images at differentoptical depths.
 3. The display system of claim 1, wherein the opticalsubsystem is configured to produce the plurality of virtual images atdifferent optical depths by directing light rays to cause light of eachof the plurality of virtual images to travel a different distance withinthe optical subsystem before exiting the optical subsystem on a path tothe viewer.
 4. The display system of claim 1, wherein the opticalsubsystem further comprises: a semi-reflective optic having a surfacedisposed at an acute angle relative to an emissive or transmissivesurface of the display; and a back reflector to reflect light reflectedby the semi-reflective optic.
 5. The display system of claim 1, whereinthe optical subsystem comprises a plurality of polarization-dependentstacks of optical layers, each stack of the plurality ofpolarization-dependent stacks of optical layers being located at adifferent position across a field of view of a viewer.
 6. The displaysystem of claim 5, wherein the plurality of stacks of optical layersconsists of two stacks of optical layers, each positioned to be in frontof a different one of a left eye and a right eye of the viewer.
 7. Thedisplay system of claim 1, further comprising circuitry to switch theplurality of polarization-dependent segments on and off.
 8. The displaysystem of claim 1, wherein the display is operable to be coupled with ahead-tracking or eye-tracking camera.
 9. The display system of claim 1,wherein the optical subsystem comprises an electro-optical layerdisposed in an optical path between the display and the left and righteyes of the viewer, and wherein polarization of light from the displayis switched by the electro-optical layer such that frames are sentalternately to the left eye and the right eye of the viewer.
 10. Thedisplay system of claim 1, wherein the display is a first display, thedisplay system further comprising a second display, and wherein thefirst and second displays produce light of different polarizations tothe left eye and right eye, respectively, of the viewer.
 11. The displaysystem of claim 1, further comprising a shield layer to prevent straylight from reaching an eye of the viewer.
 12. The display system ofclaim 1, where the plurality of polarization-dependent segments of theaperture allows the image of left eye or right eye to pass throughdepending on a location of the viewer's head or gaze.
 13. The displaysystem of claim 12, wherein an alternating polarization is provided byalternately gating stacks of optical layers for the left eye and theright eye of the viewer.
 14. A display system comprising: a display toemit or transmit light; and an optical subsystem, optically coupled tothe display, wherein the optical subsystem comprises three or morepolarization-dependent shutters positioned at different locations acrossthe field of view of the viewer, and wherein the polarization-dependentshutters are separately gated under control based on inputs from ahead-tracking or eye-tracking camera to shift polarizations across aviewable zone.
 15. The display system of claim 14, wherein the three ormore shutters are controlled in synchronization with left eye frames andright eye frames displayed by the display depending on interpupillarydistance of the eyes of user.
 16. The display system of claim 14,wherein the optical subsystem is configured so that an eyebox of theleft eye and an eyebox of the right eye of the viewer overlap andproduce a continuous image.
 17. The display system of claim 14, whereinthe optical subsystem is configured so that an eyebox of the left eyeand an eyebox of the right eye of the viewer blend and producecontinuous binocular virtual images at different depths.
 18. The displaysystem of claim 14, wherein the optical subsystem is configured toenable both stereopsis and monocular depth to be perceived by the viewerwith no need for adjustment for an interpupillary distance of theviewer.
 19. The display system of claim 1, wherein the optical subsystemis configured so that an eyebox of the left eye and an eyebox of theright eye overlap and produce a continuous image.
 20. The display systemof claim 1, wherein the optical subsystem is configured so that aneyebox of the left eye and an eyebox of the right eye of the viewerblend and produce continuous binocular virtual images at differentdepths.
 21. The display system of claim 1, wherein the optical subsystemis configured to enable both stereopsis and monocular depth to beperceived by the viewer with no need for adjustment for aninterpupillary distance of the viewer.
 22. The display system of claim1, wherein the different depths are turned on and off based on a signalin display content that is to be displayed.
 23. The display system ofclaim 1, wherein the display system is a headset.
 24. A display systemcomprising: a display to emit or transmit light; and an opticalsubsystem, optically coupled to the display, and configured to provide asingle continuous aperture that has a plurality ofpolarization-dependent segments at different locations across a field ofview of a viewer, such that a left eye of the viewer and a right eye ofthe viewer each see a different plurality of virtual images at differentdepths to produce a stereoscopic and monocular image in a continuousviewable spatial region for both eyes, and such that the display deviceis designed to be worn on a body part.
 25. The display system recited inclaim 24, wherein the device is designed to be worn as a headset. 26.The display system of claim 24, wherein the display is operable to becoupled with a head-tracking or eye-tracking camera.
 27. The displaysystem of claim 24, wherein the optical subsystem is configured so thatan eyebox of the left eye and an eyebox of the right eye of the viewerblend and produce continuous binocular virtual images at differentdepths.
 28. The display system of claim 24, wherein the opticalsubsystem is configured to enable both stereopsis and monocular depth tobe perceived by the viewer with no need for adjustment for aninterpupillary distance of the viewer.
 29. The display system of claim24, further comprising at least one of a motion sensor or a gesturesensor, in response to output of which the display system can inferinformation about motion of the viewer.
 30. The display system of claim24, further comprising cameras, such that the display system canintegrate spatial localization and mapping features.